Methods for Identifying Subterranean Tunnels Using Digital Imaging

1. A method of identifying a subterranean tunnel, comprising: obtaining wavefield data representing recordings of a propagating wavefield through a propagating volume that includes a portion of earth subsurface; obtaining a reference digital image of a portion or all of the propagating volume generated from the wavefield data, wherein the reference image has a reference sampling ratio and a reference image quality value; selecting a holographic computational method of imaging the wavefield data from a group consisting of a Kirchhoff diffraction stacking method, a Kirchhoff wave front smear method, wavefield synthesis, and wave equation-based methods; selecting a data subset from the wavefield data based on one or more parameters selected from the group consisting of field sampling, imaging sampling, and image quality; calculating a sampling ratio by dividing a number of data samples in the data subset by a number of image samples in the data subset; decimating the data subset, wherein the decimated data subset represents the sampling ratio less than the reference sampling ratio; generating a new digital image that includes a subterranean tunnel passing through at least a portion of the propagating volume based on the selected holographic computational method of imaging the decimated data subset, and parameters corresponding to the data subset selected from the group consisting of environmental parameters, legal parameters, operational parameters, financial parameters, and safety parameters, wherein the new digital image has a new image quality value greater than the reference image quality value; determining a quantitative difference measure between the reference digital image and the new digital image based on the changing of one or more parameters selected from the group consisting of field sampling, imaging sampling, and image quality; and identifying the subterranean tunnel.